A series of new isoxazolidines was prepared by 1,3-dipolar cycloaddition of different mono-substituted styrenes with 1,3-dipolar compounds that were prepared by the reaction of N-methylhydroxylamine sulfate with aromatic carbonyl substances.This synthetic pathway for the preparation of isoxazolidines was an ideal process of green chemistry.The synthetic products were 5-substituted isoxazolidines and their structures were characterized by mass and NMR (1H-,13C-,COSY,HSQC,and DEPT) spectrometry,and their bioactivity was investigated indicating that some new compounds inhibited Botrytis cinerea effectively.